Protonation Enables Durable and Efficient Water Oxidation on Commercial TiO₂/IrO₂

The oxygen evolution reaction (OER) performance of commercial TiO₂-supported IrO₂ (IrO₂/TiO₂) suffers from the high electron transfer barriers at the IrO₂/TiO₂ interface. Herein, we develop a cathodic polarization strategy to protonate TiO₂ (p-TiO₂) in a commercial IrO₂/TiO₂ catalyst. The high-density Ti³⁺-OH polaronic states on the surface of protonated TiO₂ greatly contribute to the decrease in the electron transfer barriers at the IrO₂/TiO₂ interface. As a result, the IrO₂/p-TiO₂ catalyst exhibits an ultralow overpotential of 246 ± 3 mV at 10 mA/cm² and durability over 200 h, attributed to electron compensation from Ti³⁺-OH states suppressing active Ir overoxidation. This electrochemical modification, requiring neither a complex apparatus nor high-temperature processing, establishes a new paradigm for designing high-performance anode catalysts.